Circuit protective switch



Nov. 16, 1943. Q A MATTHEWS 2,334,571

I ICIRCUIT PROTECTIVE SWITCH Original Filed May '7, 1940 2 Sheets-Sheet l ATTORNEYS- M6 Zww/J lNVENTOR J Nv. 16, 1943. G, A MATTHEWS 2,334,571

CIRCUIT PROTECT IVE SWITCH Original Filed May 7, 1940 2 Sheets-Sheet 2 i Patented Nov. 16, 1943 2.334.571' craeurr raornorrva SWITCH George A. Matthews, Detroit, Mich., assigner to The Detroit Edison Company, Detroit, Michwa corporation of New York Original application May 7, 194.0,v No.A

333,875. Divided and this application April 13,

ICE

1942, Serial No. 438,823

14 Claims. (Cl. 200-97) This invention relates to circuit protective switches and particularly to switches of the line shorting contacter type.

This application is a division of my copending application Serial No. 333,875, led May 7, 1940, Apparatus for protecting power lines, which describes and claims electrical distribution circuits that include line shorting contactors in addition to the customary protective switcheear and fuses.

The function of the line shorting contacter is l selected overload conditions, and mechanical deto short circuit the line on which a fault occurs, vices and circuit elements for preventing reclosure thereby establishing a low-resistance short oirof the switch for a predetermined period after a cuit, at a point intermediate thefault and its closure and subsequent opening of the switch. power source, of a current value equal to the full These and other objects and advantages of the short circuitcapacity of the power source obtaininvention will be apparent from the iollowineT able at the point in the circuit where the intenlspecification when taken with the accompanying tional short circuit is applied by the line shortdrawings in which: ing contacter. The heavy flow of current through Fig. 1 is a central sectionthrough a circuit prothe intentional short circuit of the shorting detective switch embodying the invention; vice results in the rapid opening of the source 2o Fig. 2 is a. schematic diagram of the same; breaker responsive to this heavy ilow of current and and not responsive to the lesser new of current Figs. 3, 4, and 5 are sectional views of the coil through the initial fault on the line before the shunting switch and time-controlled latching operation of the shorting contacter. The operamechanism. tion of the snorting contacter to short the line is The protective switch or line shorting contacter instantaneous upon fault inception. vThis instanis a fully automatic, self-contained unit housed taneous suppression of the initial fault beyond the within a -chamber comprising a hollow insulator shorting device substantially eliminates damage to I0 with upper and lower metal sleeves I I, I2, and the conductors at the fault and prevents the top and bottom closures I3, I4 that are belted te blowing oi fuses located intermediate the shortthe'sleeves Il, I2, respectively. The central poring contacter and the initial fault. Generally tion of the insulator I0 is groeved or otherwise the electrical distribution circuits are such that shaped te receive a supporting bracket I5 by the number of shorting contacter installations which the shorting contacter is mounted on a pole should not be limited. The physical layout or the at any point in a circuit. A source or line terminal geography of the circuit governs the selection of I6 enters the upper shell II through an insulatthe location or locations to be equipped with the ing bushing I1, and a load terminal I8 extends devices. The line sherting contacter supplethrough and is Welded or otherwise mechanically ments, but does not replace, other equipment Such and electricallyconnected to the shell II. The as circuit breakers, or other timing devices that operating coil I9 of the contacter is connected reclose the circuit a plurality of times and for between the terminals I6, I8 by straps Zll, 2l, reperiods of upward of 30 cycles in attempts to spectively, the coil I9 comprising asingle or mulburn off the fault or the faulty Vbranch circuit tiple layer solenoid wound from a at copper bar. in the case of a permanent fault. The reclosing The coil I9 is mounted within a laminated core operations of the conventional switchgear take 23 that is secured between a pair of supporting place in the conventional manner as the line plates 24 by bolts 25, and the plates 24 are shorting contacter includes a timing mechanism secured to and grounded on the upper metallic for preventing a second establishment of va line shell II by brackets 2'6. The central section 2l of snorting circuit after the substantially instanthe laminated core rests upon a rubber cushiontaneeus closure of the line shorting contacter and ing member 28 to serve as a stop for the plunger, the subsequent opening of the short circuit which the cushioning member being carried by a plate is placed on the line. 29 that is rigidly secured to the supporting plates An object of this invention is to provide a circuit v4. The armature er plunger 30 comprises lam- .protective switch that closes substantially` ininations riveted to ribs 30' that are welded to the stantaneously upon the occurrence of a fault on switch rod 3| and project above the laminations the line beyond it, thereby to extinguish the curto`carry a part of the control mechanism. 'I'he rent ilow beyond the switch in a time far less than heretofore attainable. .An object-is to provide a normally open switch that includes mechanism for preventing reclosure of the switch for a predetermined period after a closure and subsequent opening of the switch. More particularly, an object is to provide a normally open switch having an operating coil for'series connection in a distribution circuit to close the switch upon preconical contact 32 on the switch rod 3i is axially alined with a conicaily recessed contact assembly comprising a plurality oi.' wedge-shaped segments 33 on leaf springs 34. 'Ihe lower ends of the springs 34 are securedto a cylinder 35 on a plate 38 that is supported from the plate 29 by a plurality of insulating rods 31. A pressure contact member 38 is connected to plate 38 by jumpers 39 and pressed into engagement with the lower closure I4 by a spring 49. A terminal lug 4| projects below the closure I4 for connection to similar lugs of the shorting contactors of other phases or to the conductor of a two-wire branch other than that to which source and load terminals I6, I8 are connected. The hollow insulator is illled with oil to a level above the core 23, and a low resistance connection from the load terminal I8 to the moving contact 32' is obtained through jumpers 32 that extend from contact 32 to the plate 29.

The upper end of the rod 3| extends through a strap 42 that is fixed to the supporting plates 24, and a spring 43 is coiled about the rod 3| tohold the rod in elevated position against the closing force developed by coil I9 at current flow less than a predetermined amount, for example 50%, above rated current that the contacter can carry for long periods.

The source or line terminal I8 is connected to the stationary contact 44 of a coil-shorting switch by the strap 20 and a jumper 45. The movable switch contact 44' is carried by an arm 48 pivoted upon the supporting plates 24 and normally retained in open-circuit position by a spring 41 that is anchored to plate 24 by a bolt adjustable along slot 41'. The arm 48 is grounded on the load terminal I8 through the supporting plates and preferably is connected to the plate 24 or to lead 2| by a jumper 48, see Fig. 2. A closure of switch contacts 44, 44' will short circuit the operating coil I9 and thus prevent operation of the shorting contactor. Time-delay mechanism, indicated generally by the block 49, is provided for retaining the switch 44, 44' in closed position for a predetermined interval following a closure of the switch.

The control mechanism i'or the shorting contactor is located between the upper ends or the supporting plates 24 and comprises a mechanical linkage having parts mounted on the plates 24 and other parts pivoted to the central ribs 30' of the laminated core. The control mechanism is illustrated in Figs. 3-5 as viewed from/,a plane r through the axis of the rod 3|, except that the timing mechanism is shown in elevation in Figs. 3 to 5.

The movable contact arm 48 comprises a pair of duplicate members mounted on plates 24 by a pivot pin 5I and joined at their outer ends by a strap 46' which carries the contact 44'. A link 52, also pivoted on pin 5I, is coupled to the contact arm 48 through a hairpin spring 53 that urges the contact arm 48 clockwise when link 52 is rotated clockwise by the plunger. A pivot pin 54 connects the other end of link 52 toa latch member 55 and extends'through an elongated slot in a link.58 that is pivoted to the core plate 38'. The upper end of the latch member is cut back for locking en-gagement with a roller 51 on the pivot pin of alever 58,Y thelatch'member being pressed toward the roller 51 and a latch-releasing pin 59 on lever 58 by a spring 88. The forked outer end of lever 88 receives a pin 8| on a timing lever 82 carrying a pawl 83 that bears on ratchet wheel 84 on the shaft of an escapement mechanism of conventional type.

indicated by the block 49. Pawl 83 drives the ratchet wheel clockwise when lever 82 is rocked in that direction by a spring 85, and rides idly over the ratchet wheel when the lever is moved counterclockwise by a link 68 having an elongated slot receiving a pin 81 on the core plate 38. The core plate 38 has an inclined slot, defined by a notch in the plate and a projection 89, for receiving a roller 89on a hold-oif link 18 that is pivoted to the supporting plates 24 and urged clockwise towards a stop pin 1I by a spring 12.

The control mechanism operates in the following manner. The arm 48 is normally held in raised position by the spring 41, and the roller 89 of link 19 is seated in the inclined slot of the core plate 38', as shown in Fig. 3. A predetermined current ilow through coil I9 overcomes the spring 43 and moves the core 30 and rod 3| downwardly to close the shortin-g contactor, and the several parts then have the positions shown in Fig. 4. Link 58 moves the latch member 55 down into locking engagement with the roller 51, and rocks the link 52 clockwise to stress the spring 53 that urges the contact arm 46 towards closed position. The drop of the plunger released the roller 89 of link 10 from the slot in the core plate 30', and thereby forced link 10, in conjunction with the spring '12, clockwise to the stop 1I. This brought the upper end of link 10 into the path of the bar 48 of the contact arm 48 and thus prevented a closure of the coilshunting contacts 44, 44'. Link 86 moved the timing lever 82 counterclockwise and thereby stressed the spring 85 that is to restore the timing lever to normal position with a time-delay that is controlled by the escapement mechanism 49. The latch-release pin 59 is now spaced from the latch member 55.

Upon the ilrst opening of the circuit breakers, the rod 3| is lifted by the spring 43 and the parts assume the positions shown in Fig. 5. Link 52 cannot move up as it is locked by the engagement of latch member 55 with the roller 51, and the stress in the spring 53 tends to move the contact arm 48 clockwise to close contacts 44, 44'. This closing motion takes place as soon as the core assembly moves upwardly to force the roller 89 of link 1,0 into the inclined slot by the projection 68. The elongated slot in links 86 permits the core assembly to lift, but the counterclockwise movement of the timing lever 58 is retarded by the escapement mechanism 49 since the timing lever is locked to the escapement mechanism by the pawl 83 and ratchet wheel 64. 'I'he time-delayed return movement of the lever 58 displaces the pin 59 into engagement with the latch member 55 to force it out of locking engagement with the roller 51. When released from roller 51, the latch member 55 is moved upwardly by the spring 53 thus releasing the stress in that spring and thereby permitting the spring 41 to rock the arm 46 counterclockwise Vto open contacts 44, 44'. The equipment is thus reset to the condition shown in Fig. 3 after a time-delay determined by the escapement mechanism 49. The time-delay is sufficient, for example of the order of three minutes as explained in detail in the copending application, to permit a reclosing circuit breaker to operate through a predetermined time-delay to a lockout in the case of a permanent fault on the line.

It is to be noted that, upon the initial removal o! current by the circuit breaker, the immediate reclosure of the shorting contacter is blocked electrically by the switch 44, 44' that shunts the coil I9, and is blocked mechanically by roller 69 and its supporting link 10 that is blocked against clockwise movement by the strap 46' of the closed contact arm 48.

The critical current value for actuating the shorting contactor is determined by the number of turns of the coil I9, and the forces exerted by springs 43, 41, 53 and 65. The period of blocked operation is determined, for any given escapement mechanism, by the force developed by the spring 65 and by the gear train in the escapement mechanism. A control of the operating characteristics is readily attained by adjusting the compression of spring 43 by the downward or upward movement of the lock nuts on the end of the rod 3|. The spring 43 opens the shorting contactor in about 5 cycles after the circuit breakers of the distribution circuit open, but the exact opening time is not important since the first reclosure of the circuit breaker is delayed for from 30 to 60 cycles as a protection against multiple lightning strokes. The shorting contactor must open under no-load, however, as the simple design which facilitates an instantaneous closure makes no provision for extinguishing an arc between the main contacts.

Operating speeds oi' the order of from 2 cycles down to l@ cycle, on a 60 cycles per second distribution circuit, have been obtained in mechanically stable equipment such as shown in Fig. 1, and commercial installations have fully demonstrated that this high operating speed protects insulated conductors from burn off from transient faults and prevents the blowing of sectionalizing fuses by transient faults. The line shorting contactor does not, and is not intended to, protect the conductors against burn of! in the case of a permanent or relatively permanent fault as the shorting contactor locks out after its first operation to permit the conventional timedelayed operation of a reclosing circuit breaker or a repeater fuse assembly. The maximum service is maintained on the network, and the location of the fault is most readily ascertained, when the faulty branch circuit is isolated by sectionalizing fuses or is burned oil during the sequence of operations of a reclosing circuit breaker prior to a iinal lockout.

It is to be understood that adequate protection against burn off from transient faults may be had on some feeders when the fault current continues for more than about l/2 to 2 cycles, on a 60 cycles per second basis, but line shorting contactors of this high operating speed may be readily manufactured in accordance with this invention and there is no advantage in designing the switch for a longer operating time. The invention is not limited to the particular embodiment herein shown and described, and various changes may be made in the parts, and in their design, size and relative arrangement without departure from the spirit of my invention as set forth in the following claims.

I claim:

1. A line shorting contactor comprising a normally open switch having relatively movable contacts for connection to opposite sides of a power distribution line, electrically-actuated switch closing means, blocking means operative upon an opening of said switch to prevent reclosure thereof, and time delay means for rendering said blocking means inoperative.

2. A line shorting contactor as recited in claim 1, wherein said blocking means includes means mechanically locking said relatively movable contacts in switch open position.

3. A line shorting contactor as recited in claimV 1, wherein said blocking means includes electrical means rendering said switch-closing means inoperative.

4. A line shorting contactor as recited in claim l, wherein said blocking means includes means mechanically locking said relatively movable contacts in switch open position and electrical means rendering said switch-closing means inoperative.

5. A line shorting contactor comprising a normally open switch having relatively movable contacts for connection to opposite sides of a power distribution line, electrically-actuated switchclosing means including a coil having terminals for series connection in one side of the line, blocking means operative upon an opening of said switch to prevent reclosure thereof, and time delay means for rendering said blocking means inoperative.

6. A line shorting contactor comprising a switch having relatively movable contacts for connection to the opposite sides o1' an electrical power distribution line, means biasing said contacts to switch open position, electromagnetic means including an operating coil in series in one side of said line for closing said switch contacts, blocking means responsive to an opening of said switch contacts to prevent reclosure of said switch, and time delay means for rendering said blocking means inoperative.

'7. A line shorting contactor comprising a switch having relatively movable contacts for connection to the opposite sides oi' an electrical power distribution line, means biasing said contacts to switch open position, electromagnetic means including an operating coil in series in one side of said line for closing said switch contacts, blocking means responsive to an opening of said switch contacts to close a shorting circuit about said operating coil, thereby preventing a reclosure of said switch, and time delay means to open said shorting circuit.

8. A line shorting contactor as recited in claim 7, wherein said blocking means includes means mechanically locking said relatively movable switch contacts in switch open position.

9. A electromagnetic switch comprising an operating coil, a magnetic plunger assembly slidable within said coil and including a switch rod, a switch contact carried by said rod, a cooperating switch contact, means biasing said plunger assembly for movement to separate said contacts, means operative upon a switch opening movement of said plunger assembly to block a switch closing movement, and time delay means for rendering said blocking means inoperative.

10. An electromagnetic switch as recited in claim 9, wherein said blocking means includes means mechanically locking said plunger assembly against switch closing movement and means short-circuiting said coil.

l1. In an electromagnetic switch, an axially movable switch rod carrying a contact, .a cooperating switch contact, means biasing said switch rod for switch opening movement, a coil and plunger for moving said switch rod in the opposite direction to close said switch contacts, a normally open auxiliary switch for vshort-circuiting said coil, spring means stressed by a switch-closing movement of said plunger to bias said auxiliary switch towards closure, means locking said spring means in stressed condition, blocking means actuated by said plunger to control the closure of said auxiliary switch by said spring' means in accordance with the position of said plunger, said blocking means being actuated into and out oi blocking position by respectively a switch-closing and a switch-opening movement of said plunger, whereby said auxiliary switch can close only after a switch-opening movement oi said plunger, and time-delay means for rendering said locking means inoperative.

12. In an electromagnetic switch, the invention as recited in claim 11, in combination with latch means for mechanically locking said plunger against switch-closing movement for a period following a switch-opening movement thereof, said latch means comprising said blocking means and said auxiliary switch.

13. A line shortening contacter comprising a normally open main switch having contacts forv l connection to opposite sides of a power distribu- 

